1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer or a copying machine for producing a copy and a management system therefor which can prevent illegal copying.
2. Description of the Prior Art
Recently, copying machines and printers are developed and used widely. Then, infringement of copyrights and illegal copies of secret documents become problems to be solved. There have been proposed many apparatuses and methods in order to prevent the leakage of secret documents by copying. In an apparatus, a prescribed additional code is added or embedded in a hard copy of a document when the document is regenerated. The additional code comprises digital or discrete dots which have sizes hard to be recognized with naked eyes. When the hard copy is regenerated again, the additional data is read and if the hard copy is decided to be related to a secret document, regeneration of the hard copy is for example prohibited.
However, in many cases, a document does not become secret after a predetermined time has passed. Therefore, it is preferable that the document is allowed to be regenerated in such a system which prevent illegal regeneration by using additional data formed on a hard copy.